#include <stdio.h>
#include <ctype.h>

int strlen(const char s[]);
int atoi(char s[]);
int lower(int c);

main()
{
	char *str = "hello, world.";
	printf("%d", strlen(str));
}

int strlen(const char s[])
{
	int i = 0;
	while ( s[i] != '\0' )
		++i;
	return i;
}

int atoi(char s[])
{
	int i, n = 0;
	for ( i = 0; s[i] >= '0' && s[i] <= '9'; ++i )
		n = 10 * n + (s[i] - '0');
	return n;
}

int lower(int c)
{
	if ( c >= 'A' && c <= 'Z' )
		c += 'a' - 'A';
	return c;
}

